Bandwidth Required By Single Voip Call

Yesterday, One of my collegue walk down to me and had asked a very wonderful question that how much bandwidth is required to deliver a one voip call. I replied that go with www.voip-calculator.com. Then he rasied a point that dusing customer call I would have limited access to internet, so provide me some sort of calculation which could help me to calculate the bandwidth.
To calculate the bandwidth of voip call, calrity of codec, delay and transport media is essential. Depicted is list of Various Overhead

Data Link Overhead

Ethernet 18 Bytes
PPP 6 Bytes
Ethernet With Dot1q 22 Bytes



Network Overhead
IP 20 Bytes
UDP 8 Bytes
RTP 12 Bytes

Payload Size is 20 bytes

Lets calculate how much bandwidth is required for 3 calls, if customer is using G.729 codec and transposrt media is ethernet.

total bandwidth requirement = (total packet size*codec bandwidth requirement)/payload size

((18 Bytes of Ethernet + 20 Bytes Of IP + 8 Bytes Of UDP + 12 Bytes of RTP + 20 Bytes of Payload) * 8 Kbps G.723 Codec Bandwidth)) / 20 Bytes of Payload

(78 Bytes * 8 Kbps ) / 20 Bytes

31 Kbps

31 kbps is the bandwidth required by one call, now multiply it by 3.


regards
shivlu jain

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